(The original inquiry pertained to HVAC push button control repair, which is
covered in a separate reply)
Here are the texts of two messages I sent out recently:
#1. (This was in response to someone who noticed that the handle was
loose - this is another common problem when the Allen screw isn't put in
right, but it does not affect the switch operation).
Most likely the switch is gunked up inside. I doubt the loose handle would
have contributed - if you felt the detent of it clicking over the two
positions. However, it doesn't hurt to check it before you go to the
trouble of taking it apart. Do you have the wiring diagram so you can see
what contacts to check for continuity? It is non-intuitive - you really
need the diagram to figure out what the switch is supposed to do - it is far
from a normal switch. It not only handles the headlights, tail lights and
dash lights, it also enables the cornering lights when the parking or
headlights are on - these are all involved with extra wires/contacts. The
switch incorporates a thermal overload type circuit breaker also, as you
will see. If you find a failed contact, you should try giving the switch
guts a high colonic by squirting contact cleaner in through the handle
opening. You can really drown it, it won't hurt anything, and you may very
well bring the switch back to life without having to take it apart - if so
you'll save yourself hours of work. Squirt the stuff in there, then begin
working the handle back and forth a jillion times, watching your
continuity - you will possibly be rewarded by it coming back to life. Once
it is working on all contacts again, just frequent use will keep it working.
The dimmer rheostat is usually dirty, and that is the usual cause of no dash
lights. Contact cleaner of the type sold at Radio Shack will help, but I
also use fine sandpaper on the brass slider and the fixed connections, plus
the rotating contact around the center "axle" of the switch. As you will
see, that must make contact also for the dash lights to work. You have to
cut small strips of sandpaper and push them in through the sides of the
dimmer assembly to get at all the conductive surfaces. Be very careful to
not disturb the caterpillar looking nichrome coil, nestled in its cocoon, as
once it pops out of there, it is just about impossible to get it to lie down
again. Note also the little moving contact which gets moved only when the
dimmer is moved beyond full bright, this is what lights the courtesy lights
(grounding the contact is the same as opening a door). That little contact
is also usually oxidized and must be cleaned off.
#2.
These (headlight switches) can be repaired quite easily, if you have a good
set of tools
and some dexterity. The usual problem is that the grease used to assemble
the switch has hardened in place, and since the grease is non-conductive,
the switch will not work, or only work on only a few of it's functions. The
cure is to take it completely apart and clean the bejabbers out of it,
re-grease it with Dow Corning silicon grease, and reassemble it. You have
to drill out the two rivets that hold it together, then replace them with
small bolts/nuts when you are ready to put it back together. Be VERY
careful taking it apart, there are some tiny parts propelled by tiny springs
that will escape your notice and fly across the room if you are not
extremely vigilant!
Also, the internal circuit breaker is often out of calibration. However,
the circuit breaker is easily bypassed without even taking the switch apart,
since you can get at the CB output terminal from the outside of the switch.
Then you can simply wire in a replacement circuit breaker.
These switches come with a permanently attached harness which goes to a
multi-contact electrical plug; other wires in this plug go to the dash
dimmer switch. It does not have "prongs". The whole switch is a study in
quality electrical manufacturing technology of the late 60's - it is built
to last forever, if used frequently. It was never designed to sit for years
unused.
Good Luck - and welcome to the world of electrical repairs!
Dick Benjamin
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